Field of the Invention
The present invention relates to a columnar laminar flow generation device, as well as a method for generating columnar laminar flows.
Description of the Related Art
In such technical fields as semiconductor manufacturing, MEMS manufacturing, image display device manufacturing, ultraviolet light irradiation treatment and coating, there is a practice of controlling the ambience constant by discharging gases while introducing a replacement gas whose cleanliness level, gas type, etc., have been controlled, in order to eliminate dust and other foreign matters, eliminate active gases, and control temperature and humidity, etc.
Discharging gases containing foreign matter, etc., active gases, and gases whose temperature and humidity are not desired (hereinafter referred to as “gases to be replaced”) is difficult if a replacement gas is arbitrarily blown into the space because it only disturbs the flows of gases and generates turbulent flows. Undisturbed gas flows, or specifically gas flows where the gas flows linearly in one direction without generating any vortex, are called “laminar flows” or “one-directional flows,” and by blowing in replacement gases as laminar flows, the gases to be replaced can be discharged quickly from the space. Among different types of laminar flows, those which are generated by introducing a replacement gas by exactly the same volume as that of the applicable space and which can discharge all gases to be replaced as if they are pushed out by a piston, are called “piston flows” representing laminar flows of the highest replacement efficiency.
Normally, generating laminar flows requires that a fan filter unit comprising fans integrally assembled with HEPA filters, ULPA filters, or other high-performance filters be installed over the entire ceiling surface providing blow-out ports, while gratings, etc., be installed over the entire floor surface providing suction ports, so that structurally gases are blown out to the space and exhausted from the space uniformly from the top and bottom (Patent Literature 1).
With the conventional uniform blow-out/exhaust structure, generating laminar flows requires that a gas be pushed out at strong pressure through the high-performance filters, where the flow velocity of the gas as it is blown out through the high-performance filters reaches approx. 350 mm/sec. And, to purify air, the filters must be made thicker to accommodate higher velocities. High-performance filters used in semiconductor manufacturing have a folded structure and some thickness to reduce pressure losses, where filters of 20 to 30 cm in thickness are used.
The uniform blow-out/exhaust structure must use large, powerful fans to push out the gas at a high flow velocity of 350 mm/sec or so through the filters that are 20 to 30 cm thick. Also, a huge volume of gas is pushed out at high flow velocity throughout the ceiling surface, which requires large gas-circulation pumps as well as large-scale air-conditioning apparatuses, humidifiers, etc., for keeping the gas temperature and humidity constant. This is why clean rooms require a huge initial facility investment. Also, clean rooms operate at all times, incurring large electricity and water bills for large-scale fans, air-conditioning apparatuses, etc., as well as running costs including the cost of filters that must be replaced regularly.
Here, it should be noted that, in fields where laminar flows are used, the area of the region where gases must be replaced by laminar flows is only a fraction of the actual area where laminar flows are generated. For example, a semiconductor manufacturing plant uses a large-scale clean room in which multiple manufacturing devices are installed, but in reality, only those locations where wafers travel, or if wafers are in sealed transfer containers, only where the wafer processing device docks to the sealed transfer containers, need to be cleaned.
To control the ambience only in the region where such control is actually required, the inventors of the present invention proposed a reagent treatment cup with gas ejection ports provided near the outer rim of the top opening of the cup, where a gas is ejected toward the center of the top opening to fill the reagent treatment cup with the gas and also prevent the outside air from entering the reagent treatment cup (Patent Literature 2).